Uveitis refers to several ocular disorders characterized by intraocular inflammation, which in the aggregate are major causes of visual loss and blindness in the United States. Uveitis may affect any part of the eye;those forms affecting primarily the vitreous (intermediate uveitis), the retina and choroid (posterior uveitis), or the entire eye (panuveitis) are associated with high rates of visual loss. Because the peak onset of uveitis is in young adulthood, vision loss due to uveitis will have a disproportionately greater impact on years of potential vision lost per case than age-related eye diseases. Because most cases of intermediate uveitis, posterior uveitis, and panuveitis are chronic, treatment requires long-term therapy. Current therapy for patients with severe, vision-threatening uveitis typically involves the use of systemic medications, primarily oral corticosteroids, supplemented by immunosuppressive drugs in selected situations. No large-scale, NIH funded, multicenter clinical trials or epidemiologic studies have been performed in the area of uveitis;therefore, long-term data on the outcomes of treatment are limited. The fluocinolone acetonide intraocular implant is a recently-developed, surgically implanted reservoir of corticosteroid designed to last three years in order to provide long-term control of uveitis. Because of the potential for effective control of uveitis with minimal systemic side effects, the use of this implant may alter the way in which uveitis is treated. Therefore, a multicenter, randomized, controlled clinical trial, the Multicenter Uveitis Steroid Treatment (MUST) trial, is proposed, which will compare the fluocinolone acetonide implant to "standard therapy" for the treatment of patients with severe, vision-threatening intermediate, posterior, or panuveitis. Patients with active uveitis will be randomized to treatment with either the fluocinolone acetonide implant or "standard therapy" consisting of oral corticosteroids and supplementary immunosuppressive drugs when indicated, according to standardized guidelines. The design outcome will be visual acuity outcomes. Other outcomes include ability to control the uveitis, resolution of macular edema (a major cause of visual loss in these patients), and ocular and systemic morbidity from both the disease and the treatments. Additional benefits include prospective epidemiologic data on the long-term outcomes of uveitis, its complications, outcomes of systemic treatments for uveitis, and complications of the treatments.